When I was a kid, there were matchbox cars that changed colors, when you dipped them in hot or cold water.  Nissan is allegedly developing a color changing technology, whereby the driver can select from an array of colors, to change the car’s color. They have developed a “paramagnetic” paint coating, which is a unique polymer layer that features iron oxide particles that are applied to the vehicle’s body. When an electric current is applied to the polymer layer, the human eye then interprets the crystals in the polymer as different colors. [source]